This invention relates to an improved fluid valve for regulating the rate of fluid flow in a fluid line or passageway, and more particularly relates to a fluid valve for accurately controlling the amount of dampening fluid delivered to a nozzle for application onto the plate cylinder of an offset printing press.
In the offset printing process, high quality printing is highly dependent upon accurate control of the amount of dampening solution applied to the offset plate. It is thus highly desirable to accurately control both the rate of application of the dampening solution through the delivery system and out the nozzle and also the interruption and initiation of fluid flow.
This application incorporates by reference U.S. Pat. No. 4,064,801 by Thomas G. Switall entitled "Spray Dampening System For Offset Printing"; application Ser. No. 934,866 filed Aug. 18, 1978 by Thomas G. Switall entitled "Spray Dampening System For Offset Printing With Page Control Assembly" now U.S. Pat. No. 4,211,258, issued July 8, 1980; and application Ser. No. 945,107 filed Sept. 25, 1978 by Thomas G. Switall entitled "Spray Dampening System For Offset Printing With Page Control Assembly" now U.S. Pat. No. 4,198,907, issued Apr. 22, 1980.
The above named patent and patent applications discuss in detail the reasons for requiring precision application of dampening fluid and include descriptions of alternative adjustable fluid valves, such as a needle element within a piston operated valve closure sleeve.
Known fluid valves having the requisite quality of accurately adjustable fluid flow sufficient to maintain high quality printing in an offset printing press have heretofore required extremely close tolerances in construction and the use of various metals, and have been of relatively high cost to produce as compared with the fluid valve of the present invention.
The fluid valve according to the present invention may be constructed without the extremely close tolerances previously required and is less expensive to produce, while improving the precision control over fluid flow regulation.